Cambrian Faunas. 257 



America appears to the writer to show that the cotempor- 

 ary existence of species of Olenelloid and of Paradoxidean 

 trilobites in contiguous areas is possible, although this is not 

 necessarily an inference from the peculiar distribution of 

 these trilobites. 



As a basis for the comparison of faunas, no better stand- 

 ard is available than the indisputable succession of zones iu 

 the Paradoxides beds of Scandinavia, where the following 

 succession of Cambrian beds has been shown to exist: — 



1. Tbe Holmia (Olenellus Kjerulfi) beds. 



2. The Paradoxides beds (proper). 

 P. CElandicus zone. 



P. Tessini zone. 



P. Davidis zone. 



P. Forchammeri zone. 



Agnostus lavigatus zone. 



3. Olenus beds. 



4. Peltura beds (including the Dictyonema slates.) 



5. Ceratopyge (Dicellocephalus) beds. 



The last division is considered by the Swedish palaeontolo- 

 gists not to be Cambrian but to belong to the next system 

 (Ordovician or Lower Silurian.) 



In dealing with the subject from a more general point of 

 view it is necessary to insert another zone of Paradoxides 

 beds which is only imperfectly represented in Scandinavia 

 in the " Exsulens Kalk " at the base of the Tessini zone ; 

 this is the group of strata with P. rugulosus, which species 

 is well represented in all the Southern faunas, and in the 

 Acadian regions comes between the CElandicus and Tessini 

 zones. 



The complete series of Paradoxides beds proper, would 

 thus stand as follows : — 



a. P. CElandicus (=lamellatus) zone. 



b. P. rugulosus (=Eteminicus) zone. 



c. P. Tessini (=Abenacus) zone. 



d. P. Davidis zone. 



